Rough idle and code po304

[1989dangeroustoy]

Have a 96 ex 4.0 manual, it has a rough idle and just set a. Po304 code , I changed the plugs and checked the wires with no change, I also cleaned the Maf and Icv, I have no coolant loss and no tailpipe smoke ... I've been reading online but haven't found any good info. Suggestions would be greatly appreciated I don't Want to dump anymore unnecessary cash into this thing

 

[1989dangeroustoy]

It also high idles to 1500 when I come to a stop and then drops down to 1000 after a few seconds

 

[MrShorty]

I'm not real good with OBD-2/EEC-V diagnostics. P0304 means that the computer detected a misfire on cylinder 4. The first question I would ask is if the misfire is really isolated to #4 or if all cylinders are misfiring and, for whatever reason, the computer decided #4 was the worst. Is the P0304 consistent, or is it sometimes P0304, then P0302, then P0300.

If it's a misfire specific to #4, then you need to look at all the things specific to cylinder that could cause a misfire (ignition components, valves, compression, injector, etc.). When you changed the sparkplugs, did the #4 plug look different from the others? Did they show any signs of fouling?

If you decide it's more of a general misfire, then you need to poke around at different things than cause misfires (which could be a lot of different things).

On edit: One of the first things I think of with a high idle is a vacuum leak.

 

[1989dangeroustoy]

No po304 is the only code, I tried swapping the 3 and 4 wire on the coil and cleared the code, no change, same code came back, spark plugs all look the same

 

[1989dangeroustoy]

I'm going to pull the upper intake today and mess with the injectors and pull the valve Cover on the driver side I've got some valve noise in there anyway

 

[greasemanicure]

I went through the same routine you are planning to do to clear the P0304 I had that was not cleared by changing plugs, wires and coil pack. Used an old timing light to check for spark on the cylinder 4 wire and did not show spark. Changed wire as you did with still no spark to #4. After all the work I came back to the plug in #4 and found the new one I put in was dead short. Just had this happen again and same thing on the Autolite platinum that I put in 12-15k ago. Happy hunting.
Joe